Landscape photographers know that filters are very important to their work, but some of those filters can be very useful in other types of photography too.
One of their most important filters is the ND, or Neutral Density filter. So what about it?
A ND filter, particularly a 10 stop filter is sort of a specialized item. You can't use it mounted on your lens for everyday photography. It basically acts like a piece of welding glass as it cuts down the light that enters the lens. Why would you want that? Long exposure photography is one important reason. Many beginners’ associate long exposures with nighttime and one of the reasons could be failed long exposure attempts during the day.
The truth is it's impossible to get a one minute or more exposure in broad daylight, no matter how much you close your aperture or lower the ISO. That's where a 10 stop ND filter saves the day. By reducing the amount of light with ten stops, it allows you to get very long exposures even if the sun outside barely allows you to look at anything without sun glasses.
So why not buy a cheap piece of welding glass instead? Well, you could and you would get a similar effect. But ND filters and welding glass both affect colors. However if you shoot the same scene with both of them, you will notice richer and more accurate color in the shot taken with the filter.
(Success Tip: How even hobbyists can turn photos of people into profit)
I'll leave you to Bryan Peterson for a very practical demonstration of how 10 stop filter works, in a video made by AdoramaTV.